Your gut microbiome — a collection of trillions of microorganisms inhabiting your intestinal tract — has wide-ranging effects on your health. Your unique mix of bacteria, fungi, parasites, and viruses reflects your genes, your age, the medications you take — but most of all, what you eat.
Over the past two decades, numerous studies have explored how gut microbes and their breakdown products (metabolites) affect factors linked with heart disease. For the most part, the findings support the same basic advice health experts recommend: Follow a mostly plant-based eating pattern, and cut back on highly processed foods. Doing so can help promote a more diverse, healthier microbiome.
"The standard American diet — appropriately called SAD — features a lot of processed foods that are high in sugar, artificial sweeteners, and unhealthy fats," says Dr. Uma Naidoo, director of nutritional and metabolic psychiatry at Harvard-affiliated Massachusetts General Hospital. This nutrient-poor diet can lead to dysbiosis, an overgrowth of harmful microbes. When bad microbes thrive in the gut, they form pro-inflammatory breakdown products and toxins, Dr. Naidoo explains. The resulting low-grade, bodywide inflammation contributes to obesity, poor mental health, diabetes, and cardiovascular disease.
Animal vs. plant-based foods
One metabolite of interest is trimethylamine (TMA), which is created when gut microbes feed on choline, a nutrient found in red meat, fish, poultry, and eggs. In the liver, TMA gets converted to trimethylamine N-oxide (TMAO). While some research suggests a link between TMAO and artery-clogging plaque, the evidence isn't consistent. Still, the advice to limit red meat consumption — the main source of TMA in the diet — makes sense.
But according to Dr. Naidoo, there's no need to avoid those animal-based foods, which most Americans aren't especially keen on doing. Instead, people should focus more on what they're not eating — namely, fruits, vegetables, and whole grains.
Eating fermented foods may help dampen inflammation in the body. When shopping, look for the words "contains live cultures" when choosing yogurt or kefir, a yogurtlike drink with a tart flavor and a thinner consistency than yogurt. While both products are usually made with dairy milk, they also come in nondairy versions made from almond, coconut, or oat milk. Another beverage, kombucha, is a fizzy, tart, slightly sweet drink made from fermented tea that's often flavored with fruits and herbs. Look for brands without added sugar.
For fermented products made from vegetables, look in the refrigerated section and check for the words "naturally fermented" on the label. When you open the jar, check for telltale bubbles in the liquid, which signal that live organisms are inside. Most supermarket pickles are preserved with vinegar and not made with a natural fermentation process using water and salt. For sauerkraut (pickled cabbage), choose raw or nonpasteurized products. If you're a fan of spicy food, try kimchi, a spicy, reddish fermented cabbage dish from Korea made with a mix of garlic, salt, vinegar, and chili peppers. From Japan, there's miso (a strong, salty paste made from soybeans fermented with brown rice) and tempeh (a firm, chewy product made from fermented soybeans).
Diversify your diet
A woefully small percentage of adults — only about 10% — eats the recommended daily amount of fruit (one-and-a-half to two cups) or vegetables (two to three cups). Don't limit yourself to only a few favorites like apples or broccoli, says Dr. Naidoo. "Eat a wide variety of different fruits and vegetables on a regular basis to bring biodiversity to your microbiome," she says.
Despite a recent uptick, whole grains make up less than 16% of the average American's total grain intake. Whole grains such as oats, quinoa, spelt, and barley are healthier choices than most "whole-wheat" bread, which isn't always made with 100% whole grains. Other foods that promote gut health include beans, lentils, nuts, and seeds.
Fruits, vegetables, beans, and whole grains are good sources fermentable or prebiotic fiber, which gets broken down by bacteria in your colon to form short-chain fatty acids. These compounds then circulate through the bloodstream and interact with receptors on cells that quell inflammation. These fatty acids also appear to play a role in keeping blood sugar, blood pressure, and cholesterol levels in check.
You can also increase good gut bacteria levels by consuming probiotics, which are found in fermented foods (see box). "Try adding a little bit of these foods to your meals and then grow from there," Dr. Naidoo suggests.
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